Block change Tracking (BCT) in Oracle 19c – CTWR

Description:-

In this article we are going to see use of Oracle Block Change Tracking concept in 19c database.

  • Oracle 10g introduced the Block change tracking (BCT) feature which is used to Speed up Rman Incremental Backup.
  • After Enabling this feature records the modified since last backup and stores the log of it in a block change tracking file using the CTWR (Change Tracking Writer) process.
  • Records the modified since last backup and stores the log of it in a block change tracking file.
  • Block change tracking feature is not reading the entire database blocks it just directly reads only changed blocks results in block change tracking file.
  • During backups Rman uses the log file to identify the specific blocks that must be backed up.
  • It improves the Rman performance as it is not scan whole datafiles instead of read the changed blocks and take backups .

Step 1: Enable Block Change Tracking and Check the status.

SQL> alter database enable block change tracking using file ‘/u01/clone/datafile/blockfile.log’;

SQL> Select filename,status from V$block_change_tracking;

Step 2: To check the change tracking writer(ctwr) process started or not.

SQL> select sid,program,status from v$session where program like ‘%CTWR%’;

Step 3: Disable block change Tracking.

SQL> alter database disable block change tracking;

Database altered.

SQL> select sid,program,status from v$session where program like ‘%CTWR%’;

no rows selected

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